102 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1938 



Instead of St. Katherine, it was decided to locate a station in south- 

 western New Mexico. This location seemed to partake of the clima- 

 tological advantages of Old Mexico. Our other stations, both north- 

 ern and southern, have all had relatively bad observing conditions 

 in the months December to March. In Old Mexico and southwestern 

 New Mexico, on the contrary, these months promise to be the most 

 cloudless of all. 



A. F. Moore has located the new station on Burro Mountain near 

 Tyrone, N. Mex., at a level of about 8,000 feet. The living conditions 

 there seem to give promise of being quite as attractive as at Table 

 Mountain. It lies not far from four fair-sized towns, the people of 

 the vicinity are helpful and pleasant, and the United States Forest 

 Service is exceedingly helpful and welcoming regarding the project. 

 It is hoped to be ready to observe in October or November 1938. 



With two pleasant stations besides Washington in the United 

 States, and one more isolated one in Chile, it seems feasible to rotate 

 the observers hereafter without undue privation. 



The stations at Table Mountain and Montezuma have continued 

 to observe the solar constant of radiation daily, when possible. 



ULTRAVIOLET SOLAR RADIATION 



Having failed thus far to obtain sufficient financial support to oper- 

 ate enough solar-constant stations to determine adequately the varia- 

 tion of the sun on every day of the year, as referred to in last years 

 report, it has been hoped to accomplish in some other way a program 

 of measuring solar variation as influencing weather. Several possi- 

 bilities exist. For recent years, in America, England, and Australia, 

 records of atmospheric ionization at great altitudes are being obtained 

 by several institutions and individuals. The ionization is thought 

 to be dependent on solar radiation, far in the ultraviolet spectrum, at 

 wave lengths less than 1000 angstroms. Results seem to indicate 

 that these rays vary over a great range, perhaps as much as 500 

 percent. It is hoped that these measurements may be correlated 

 with weather. 



Inasmuch, however, as both theory and our preliminary observa- 

 tions indicate that the variation of the sun, which is only of the 

 order of 1 or 2 percent in the total radiation, may be as great as 

 15 or 20 percent at ultraviolet wave lengths about 3300 angstroms, 

 it was hoped that automatic sounding balloon methods might be 

 developed whereby the variation of the sun's radiation in this part 

 of the ultraviolet spectrum could be measured accurately enough for 

 weather predicting. To this end the Smithsonian Institution made 

 two grants in aid to Dr. Brian O'Brien, of Rochester, N. Y. Dr. 

 O'Brien, aided also by the University of Rochester and by several 



